Fix reverse fall on the balcony

[eestere]

I have cast a balcony and managed to get a slight backfall in one area (about 0.4m2). Every time it rains, a damp spot appears on the wall because of it. Now I'd like to fix the backfall but am a bit unsure of which material to choose. The balcony is cast in K37 S4 with air. These are the options I have considered: Self-leveling compound Weber 4040 (a type of floor leveling compound) Cement+sand I am very grateful if someone can guide me so I can fix the problem this weekend!

 

[thomasx]

One alternative might be to sand the surface so you get the slope right.

 

[Jimmy N]

Buy Ardex A46 and level out the slope, when it has started to set, smooth the surface with a trowel. Do not sand the tile, it will only become pitted and ugly!